Switch to TOML for configuration

cli/src/bin/task.rs

@@ -2,7 +2,7 @@ use std::process::exit;
 
 pub fn main() {
     if let Err(err) = taskchampion_cli::main() {
-        eprintln!("{}", err);
+        eprintln!("{:?}", err);
         exit(1);
     }
 }